Sick chicken

One of my hens is not chasing food the way she normally does, is tired, not staying with the flock, mouth breathing. She also has been laying soft eggs. They all get oyster shells and plenty of grit. I just bought antibiotic and wormer. I haven't given either one yet. Any help would be appreciated

Try feeding her crushed egg shells. My hens prefer that to the oyster shell. Layers of soft eggs can have problems with their shell gland, or not be absorbing the calcium well. That can lead to eggs breaking inside, and is one cause of egg yolk peritonitis. Has she lost weight in her breast muscles or had trouble walking? This can be common in hens especially after a couple of years. Have you seen egg-like material in her poop, or yellow droppings? Here is some reading:

Thanks for the advice. I also have my big flock friend who told me that my hens were stressed out from an ever more aggressive roo. I have a set in the incubator plus a dozen for a friend,so I moved him out. My girls are already looking better. I feel very bad, because I leave for work long before sunrise. My honey has been telling me that they were getting beat up but I wasn't paying attention.( Were have I heard that?) Anyway I am always looking to learn.
I also like to feed them shells mixed with yogurt or oatmeal, but if I'm not the one making the eggs the shells don't always get saved.